- #1
megadethized
- 3
- 0
Hi,
i have a question about the center of mass change during photon emission in terms of the polarization of the emitted photon.
first, a few facts are as follows:
i) selection rule: if delta m=0, that means p (atomic recoil) = p (photon) in magnitude. This is of pi transition and emitted photon is linearly polarized.
ii) selection rule: if delta m=+1 or -1, that means p (atomic recoil) = 0 and emitted photon has +h/2*pi or -h/2*pi momentum. This is of sigma transition (two sigma polarizations) and emitted photons are spherically polarized.
my question is:
in case I, the center of mass (COM) of the atom changes, cause according to simple mechanical theory, we know that "a source emitting a spherical wave cannot recoil, because the spherical symmetry of the wave prevents it from carrying any linear momentum from the source, thus the COM of the atom changes". What about the second case? Due to the existence of atomic recoil, can we say that the COM remains invariant?? in other words, if an atom emits linearly polarized photon after delta m=+1 or -1 transition, the COM remains unchanged? the case I is true, i only wonder about the case 2.
thanks
Berkay
i have a question about the center of mass change during photon emission in terms of the polarization of the emitted photon.
first, a few facts are as follows:
i) selection rule: if delta m=0, that means p (atomic recoil) = p (photon) in magnitude. This is of pi transition and emitted photon is linearly polarized.
ii) selection rule: if delta m=+1 or -1, that means p (atomic recoil) = 0 and emitted photon has +h/2*pi or -h/2*pi momentum. This is of sigma transition (two sigma polarizations) and emitted photons are spherically polarized.
my question is:
in case I, the center of mass (COM) of the atom changes, cause according to simple mechanical theory, we know that "a source emitting a spherical wave cannot recoil, because the spherical symmetry of the wave prevents it from carrying any linear momentum from the source, thus the COM of the atom changes". What about the second case? Due to the existence of atomic recoil, can we say that the COM remains invariant?? in other words, if an atom emits linearly polarized photon after delta m=+1 or -1 transition, the COM remains unchanged? the case I is true, i only wonder about the case 2.
thanks
Berkay